The present invention relates to a bonded metal-ceramics material or member and how to bond them together. In particular, the invention concerns a material or member which consists of alumina, magnesia or spinel and an aluminum alloy bonded together and how to bond them together.
As disclosed in JP-A-60-71597, JP-A-62-72577 and JP-A-62-182166, the bonding of alumina to metal is conventionally achieved by inserting between the surfaces of the alumina and metal to be bonded together a three-layer insert material that consists of a core material made of aluminum or an aluminum alloy and skin materials made of an aluminum-silicon matrix alloy and pressing them together at a temperature that is not lower than the solidus of the aluminum-silicon matrix alloy forming the skin materials but not higher than the melting point or solidus of the core material. As disclosed as well, the Al--Si matrix alloy mentioned above may be any desired Al--Si--Mg alloy. These traditional methods are not only common in terms of the structure of the insert material used, but also make use of a bonding temperature that is not lower than the solidus of the Al--Si matrix alloy forming the skin layers of the insert material.
Moreover, JP-A-60-71597 teaches that the reason for using an Al--Si--Mg alloy for the skin layers of the three-layer insert material is that Mg is effective for improving the wettability of an Al--Si matrix alloy melt with respect to alumina and Fe.
Such aluminum-alumina bonding has so far been considered to be due to chemical reactions such as the reduction of alumina or impurities contained in it by an Al melt or mechanical actions caused as by an anchoring action of micropores on the surface of alumina, but these considerations appear not to be accurate.
Some plausible mechanism of how bonding takes place is still unclarified as mentioned above, but it is somehow possible to achieve the bonding of alumina to metal by conventional methods.
However, when the bonding of alumina to metal is carried out at a temperature not lower than the solidus of the Al--Si matrix alloy forming the skin layers of the insert material, as done in the prior art mentioned above, there are some problems. For instance, the insert material is placed under insufficient thickness control, making unstable the relaxation of thermal stress occurring due to a difference in the coefficient of thermal expansion between alumina and metal. In addition, a melt of the Al--Si matrix alloy forming the skin layers of the insert material reacts directly with the surface of the metal element to be bonded at the bonding temperature, thus between the Al--Si matrix alloy and the metal there can be formed a brittle intermetallic compound layer, which may and fail to give rise to microcracks during cooling, and fail to give an airtight bonded interface. One approach to solving these problems is to make the thickness of the insert material larger than 2 mm, as set forth in JP-A-62-72577. Another approach is proposed in JP-A-62-182166, in which a Cr layer or a layer composed mainly of Cr is provided on the surface of the metal to be bonded.
One object of the invention is therefore to provide a bonded metal-ceramics material having an airtight bonded interface and a simple method for bonding them together, inter alia, to provide a bonded alumina-metal material and a method for bonding them together and to provide a metal-ceramic composite structure in which the bonded metalalumina material is further bonded to another metal material.
Another object of the invention is to provide a bonded metal-ceramics material having a bonded interface of high strength and excellent airtightness and a simple method for bonding them together, inter alia, to provide a bonded magnesia or spinel-metal material and a method for bonding them together and to provide a metal-ceramics composite structure in which the bonded metal-magnesia or spinel material is further bonded to another metal material.